The invention relates to a measuring probe and to a measuring instrument, as well as to a method for determining the physical stability of emulsions and dispersions.
Emulsions and dispersions are among the most important of industrial merchandise, and are used in a very wide variety of fields. Since the manufacturers have to guarantee a certain degree of stability for their products, a reliable and fast method for predicting the stability of emulsions and dispersions would be of interest to them.
To date, the most widespread method for determining the physical stability of emulsions and dispersions has involved visual assessment of the samples by a person skilled in the art during storage in air-conditioned cabinets. The disadvantages of this method include the long delay between the time when the samples are produced and the time when precipitation can first be detected by eye, the degree to which the assessment depends on the particular person skilled in the art carrying out the examination, and the fact that the result lacks quantifiability. Furthermore, slight de-mixing or phase segregation in emulsions and dispersions cannot be picked up visually.
One object of the present invention is to provide a measuring probe and a measuring instrument for determining the physical stability of emulsions and dispersions which avoids the aforementioned disadvantages and, in particular, delivers quantifiable results that do not depend on an individual carrying out the measurement; a further object is to provide a suitable measurement method.
The object is achieved by a measuring probe for determining the physical stability of emulsions and dispersions, constructed from a rod comprising a material which is electrically nonconductive at least on the rod surface, which carries at least two conductivity-measurement electrodes separated from one another along the rod, these electrodes being separately supplied with electricity via the interior of the rod at one rod end.
According to another aspect of the invention, a measuring instrument for determining the physical stability of emulsions and disperses includes a measuring probe according to the invention which is arranged vertically in a sample container. An AC voltage is supplied to the conductivity-measurement electrodes, and using a Wheatstone bridge layout, the conductivity for the individual conductivity-measurement electrodes is obtained. A display device displays the results. The measuring instrument may include a computer for controlling measurement display and evaluation of the measurements, and for storing the data obtained. According to still another aspect of the invention, a method for determining the physical stability of emulsions and suspensions includes immersing a memorizing probe according to the invention in a sample container that contains an emulsion or dispersion. The conductivity of the emulsion or dispersion is the measured continuously or at intervals over a given period of time using the conductivity-measurement electrodes may be used to determine and record the time variation of the conductivity difference.